In response to public calls from the US President, Congress, Surgeon General, and a recent NIMH-co- sponsored Suicide Research Prioritization Agenda, the proposed research will examine how suicidal ideation and attempts develop within one of the most vulnerable populations at risk for suicide (i.e., adolescent girls). This work will examine how girls' atypical acute stress responses to interpersonal stress at physiological, genomic, and behavioral units of analysis moderate the association between actual experiences of interpersonal stress and suicidal ideation among girls with distal suicide risk factors (i.e., elevated depressive symptoms/lifetime interpersonal adversity). Moreover, this research will examine how these distal risk factors transact with pubertal processes to produce risk for atypical acute stress responses. Last, inhibitory control will be examined as a moderator of the association between suicide ideation and suicide attempts. This research will identify numerous biomarkers of suicide risk, significantly advancing progress towards identification and prevention of an enormous public health issue that has been woefully understudied and for which no evidence- based approaches exist. Using a combination of a RDoC conceptual framework, experimental lab-based stressor paradigm, biological assays, performance-based assessments of executive function, longitudinal methods, and innovative bioinformatics approaches for measuring gene expression, this work offers a substantial advance within a field that almost exclusively has relied on cross-sectional, single-informant, retrospective reports of suicidality. Participants will include 200 girls (age 9-14 years) at pre-, peri-, and post-pubertal stages of development. Recruitment will oversample girls with elevated depressive symptoms/lifetime interpersonal adversity to participate in a lab-based study involving the assessment of physiological, genomic, and behavioral responses following an experimentally-induced social stressor. A multi-wave assessment occurring over a one-year longitudinal interval will be conducted to obtain extensive data on suicidal ideation and attempts over time. Biological data will be collected to measure the autonomic nervous system, hypothalamic-pituitary-adrenal axis system, gene expression (using microarray-based genome-wide transcriptional profiling), and pubertal development. Ongoing research conducted by this investigative team utilizing many of the same recruitment, data collection, and analytic procedures strongly supports the feasibility of the proposed research.